(1) Field of the Invention
This invention relates to an antistatic resin-forming composition, and an application thereof.
This resin-forming composition is useful for various shaped articles, which include, for example, a protective layer of an optical recording medium.
(2) Description of the Related Art
Optical recording mediums include a writing type optical disc and an optical disc of the type for the exclusive use of reproduction. Substrates of these optical discs are made of inorganic glass or organic resins such as an acrylic resin and a polycarbonate resin. These materials are electrically insulating and readily electrically charged, and therefore, dust is readily collected on the substrate with the result of an erroneous reading of the recording mediums.
To impart an electrostatic property to the substrate, an attempt has been made wherein an antistatic agent is coated on the surface of the substrate upon which light is incident (Japanese Unexamined Patent Publication No. H3-49053). More specifically, a resin composition comprised of the same resin as that of the substrate and 2 to 10% by weight, preferably 3 to 6% by weight, based on the resin of an antistatic agent is coated as a protective layer on the substrate.
The conventional protective layer containing an antistatic agent has, however, a problem such that, when the amount of the antistatic agent added is increased to enhance the antistatic effect, the protective layer becomes undesirably pliable, and in contrast, when the amount of the antistatic agent is reduced to enhance the hardness of the protective layer, the antistatic effect is reduced. The conventional protective layer has another problem such that it exhibits an antistatic effect to a considerable extent under high humid conditions, i.e., at a relative humidity of 50% or higher, but only to a slight extent under low humid conditions, i.e., at a relative humidity lower than 50%.